Compostable hot melt adhesive

ABSTRACT

A hot melt adhesive comprises a polylactide homopolymer or copolymer, such as polylactic acid; sulfonated copolyester; and at least one plasticizer, and is compostable. The plasticizer may be a solid plasticizer, such as a benzoate, and a second plasticizer may also be used. The adhesive is suitable for use in a variety of applications, such as case and carton applications, use with burlap or other compostable substrates for tree bulbs or plant seeds, and use with other compostable films, and is especially appropriate for dual-walled paperboard beverage cups. The adhesive demonstrates good bond performance comparable to non-compostable adhesives over a range of temperatures, reflective of the temperatures of hot and cold beverages.

FIELD OF THE INVENTION

This invention relates to a hot melt adhesive which can be composted andis especially adapted for use as an adhesive for paperboard beveragecups, for both hot and cold beverages.

BACKGROUND OF THE INVENTION

Hot melt adhesives are used for a wide variety of commercialapplications. One advantage of hot melt adhesives is that these systemsrequire no carrier fluid or solvent for application to a substrate and,as a consequence, the need for subsequent evaporation of solvent orcarrier fluid is eliminated. The lack of a drying or evaporation stepallows hot melt adhesive systems to eliminate the hazards associatedwith the use of solvents and the environmental impact of volatileorganic compounds (VOCs). The use of hot melt adhesives also reduceswater consumption by not requiring water as part of the adhesive. Hotmelt adhesive formulations can be varied over a wide range of adhesiveproperties from pressure sensitive to non-pressure sensitive.

Hot melt adhesives have traditionally been based on petroleum basedpolymers. Thermoplastics have been used as the polymer component of hotmelt adhesives, which generally fall into three types: (1) petroleumbased polymers such as polyethylene, polypropylene, ethylene-vinylacetate, styrene block copolymers (e.g. styrene isoprene styrene,styrene butadiene styrene); (2) polyurethanes; and (3)polyester/polycarbonate materials.

Many of these products have the disadvantage of poor environmentaldegradability. There is a strong need for packaging materials in whichrenewable resource materials like paper, starch, and certain degradableplastics (aliphatic polyesters, polylactides, etc.) are used. In thecase of paper products, use of environmentally degradable adhesiveswould allow composting of the adhesive, when the paper, paperboard, orcardboard product is recycled. Or, alternatively, use of environmentallydegradable adhesives would allow for composting of the entire assembledarticle, unlike articles sealed with typical petroleum-based hot meltformulations.

Certain adhesive applications have more demanding requirements thanothers, and an adhesive which is compostable and performs in apaperboard beverage cup must perform several functions. For an adhesiveto be used to seal a paperboard beverage cup, it must be able to performas an adhesive over a range of temperatures, given that the cup mightcontain a cold beverage, such as juice or soda, or a hot beverage, suchas coffee or tea. For example, the adhesive must meet a performancerequirements in which the cup is filled with hot water (e.g., about 180°F.-190° F.) and is torn, then the result must be a 100% fiber tear onall seals (both radial and end seals) of the adhesive. In other words,there must be no cohesive or adhesive failure; the cup must tear first.Moreover, this test must be passed both after initial (off-line) andunder aged conditions (i.e., five days at 72° F.). In addition, theadhesive must be compostable, without compromising its bond performance.Furthermore, it would be desirable to allow the hot melt adhesive to runon existing hot melt adhesive application equipment, meaning that itmust have similar flow characteristics, including viscosity, at theapplication temperature.

Hot melt adhesives have been used to bond together the outside wall of adisposable paper cup used to contain beverages such as coffee or tea andanother substrate (e.g. paper/label), which serves as a secondary wall.To bond a cup to a label, it has been known to apply multiple radialbeads of the hot melt adhesive around the outer periphery of the cup anda seam bead (or end seal) along the length of the cup where the edges ofthe label meet. There is no known compostable hot melt adhesive in themarket today that has acceptable heat resistance to hot-beveragesconditions, such as at 180° F.-190° F. There is also no knowncompostable hot melt adhesive in the market today with wide servicetemperatures e.g., (0° F.-160° F.).

U.S. Pat. No. 5,753,724 discloses a hot melt adhesive composition thatis made using a polyester derived from lactic acid. A thermoplasticresin grade polyester is formulated into a functional adhesive usingadhesive components. A lower molecular weight material can be used as atackifying resin with a biodegradable/compostable resin in a formulatedhot melt adhesive. The adhesive material can be made pressure sensitiveand can be made entirely degradable by combining the polyester polymerwith other biodegradable/compostable ingredients. The resulting adhesivecomposition can be used in a variety of applications. Thebiodegradable/compostable adhesive material can be used as a substitutefor non-biodegradable materials made from commercial polymers thatresist attack by bacteria, fungi, and other microbial populations. Thehot melt adhesives can be used in packaging and in the manufacture ofdisposable articles which are made from degradable materials. The entiredisposable article can be made from adhesives and structural materialsthat are fully compostable.

U.S. Pat. No. 7,868,101 discloses a method for preparing anenvironmentally degradable polymeric compound as well as to such acompound per se and to its use. A compound of the present inventionincludes a polycondensated lactic acid containing polymer, having amolecular weight (Mw) of from 500 to 50,000 g/mol, to which aflexibilizing aliphatic polyester having a molecular weight of from 500to 50,000 g/mol is coupled. The amount of lactic acid including groupsin the polymeric compound ranges from 50 to 99% and the amount offlexibilizing polyester groups ranges from 1 to 50%.

SUMMARY OF THE INVENTION

Embodiments of the present invention avoid many of the issues andconstraints of the prior art. One embodiment of the invention isdirected to a compostable hot melt adhesive suitable for use in avariety of applications, such as case and carton applications, and isespecially appropriate for dual-walled paperboard cups. The hot meltadhesive composition of this embodiment comprises a polylactidehomopolymer or copolymer; sulfonated copolyester; and a plasticizer, andis compostable. The polylactide homopolymer or copolymer may be selectedfrom the group consisting of polylactic acid and copolymers of lactones,preferably glycolide and caprolactone. The plasticizer is preferablysolid and may comprise a benzoate, preferably 1,4-cyclohexane dimethanoldibenzoate. The adhesive composition may comprise a second plasticizer,which may be selected from at least one of ethylene glycol, propyleneglycol, and polyethylene glycol. The adhesive composition may alsocomprise an anti-oxidant, such as a hindered phenol. In an embodiment,the adhesive composition does not contain more than 5 wt %, morepreferably no more than 4 wt %, and most preferably no more than 3 wt %of a constituent having a hydroxyl number greater than 100 mg KOH/g.

According to another embodiment of the invention, a method for forming adouble-walled container comprises the steps of:

-   -   (a) applying the inventive hot melt adhesive composition        described herein in a molten state to the outer surface of a        first generally cylindrical paperboard substrate;    -   (b) mating a generally rectangular second paperboard substrate        to the first paperboard substrate, wherein the second paperboard        substrate is longer than the circumference of the first        paperboard substrate, thereby providing an axial strip at which        the ends of the second paperboard substrate overlap; and    -   (c) applying the hot melt adhesive composition in a molten state        to one of the mating surfaces of the axial strip; and    -   (d) mating the mating surfaces of the axial strip to provide the        double-walled container.

Another embodiment of the invention is directed to the container formedby the inventive method as described herein. In an aspect of thisembodiment of the invention, the paperboard used for the container iscompostable and the container is a beverage cup.

Embodiments of the invention provide a compostable hot melt adhesivewith bond performance and heat resistance properties similar totraditional, non-compostable hot melt adhesives, such as those based onpolyolefins, ethylene vinyl acetate, or styrene block copolymers.Adhesives according to the invention are useful in a variety of endapplications, such as case and carton applications, use with compostablefilms, use with tree bulbs or plant seeds wrapped in burlap or othercompostable substrates, and construction of various articles, such asthe construction of dual-walled beverage cups. With respect to its usein the construction of compostable dual-walled beverage cups, theadhesive may be used bond together the outside wall of an innersubstrate of a disposable paper cup and another, outer substrate (e.g.,paper/label), which serves as a secondary wall. Also, the same adhesivemay be used to both bond the inner substrate to the outer substrate andto bond together the outer substrate to itself at the end-seal area ofthe secondary wall.

Other features and advantages of the invention may be apparent to thoseof ordinary skill in the art upon reviewing the following description.

DETAILED DESCRIPTION OF THE INVENTION

According to an embodiment of the invention, a hot melt adhesivecomposition is compostable and comprises a polylactide homopolymer orcopolymer; sulfonated copolyester; and a plasticizer.

The polylactide homopolymer or copolymer is selected from the groupconsisting of polylactic acid and copolymers of lactones, preferablyglycolide and caprolactone. In a preferred embodiment, the polylactidehomopolymer or copolymer comprises, consists essentially of, or consistsof polylactic acid. In other embodiments, the polylactide homopolymer orcopolymer has a melt index of at least 50 g/10 min, preferably at least55 g/10 min, and most preferably at least 60 g/10 min at 210° C. using a2.16 kg weight in accordance with ASTM Method D1238. At most, thepolylactide homopolymer or copolymer has a melt index of 500 g/10 min,preferably at most 200 g/10 min, more preferably at most 150 g/10 min,and most preferably at most 100 g/10 min at 210° C. using a 2.16 kgweight in accordance with ASTM Method D1238.

In embodiments, polylactide homopolymer or copolymer comprises at least20 mole percent of the lactide comonomer. The general structure of thepolylactide is shown below:

Suitable polylactide homopolymer or copolymer for use herein may have anumber average molecular weight (Mn) within the range of 3,000 to200,000 g/mol. (All molecular weights mentioned herein are measured bygel permeation chromatography (GPC) using polystyrene standards.) Whilepoly(D,L-lactide) and the meso—are essentially amorphous,poly(L-lactide) and poly(D-lactide) is crystalline in nature and has acrystalline melting point of 186° C. depending on its molecular weightand stereopurity. The polymers may be prepared by ring-openingpolymerization of the bimolecular cyclic ester of lactic acid with acidor base catalysts such as PbO, SnCl₂, SnCl₄, ZnCl₂, SbFs, Sb₂O₃, ortriethylamine using solution, precipitation, or melt processes.Alternatively, they may be obtained commercially from Henley Chemicals,Inc. under the Resomer® tradename; from Poly Sciences Inc., or fromEcological Chemical Products Company (EcoChem).

In addition to homopolymers of poly(L-lactide), poly(D-lactide),poly(D,L-lactide), and poly(meso-lactide) are suitable polylactidehomopolymer or copolymer for use herein and may also be prepared bycopolymerization with other lactones such as glycolide or caprolactone.Poly (D,L-lactide-co-glycolide) polymers containing equimolar amounts ofthe lactide and glycolide components are available from Henley chemicalsas Resomer® RG502, 503, 504, 505 and 506 and are suitable for useherein. In addition, poly(D,L-lactide-co-glycolide) polymers known asResomer® RG752, 755 and 756 containing 75% of the lactide component aswell as the Resomer® 858 polymer which contains 85% lactide are alsosuitable.

In one embodiment, the polylactide homopolymer or copolymer is athermoplastic resin derived from renewable resources. Preferably, thepolylactide homopolymer or copolymer is amorphous and has a low meltingpoint. In embodiments of the invention, the specific gravity of thepolylactide homopolymer or copolymer is between about 1.1 and about 1.5,preferably between about 1.15 and about 1.4, and most preferably betweenabout 1.2 and about 1.3, according to ASTM D792. In embodiments of theinvention, the glass transition temperature of the polylactidehomopolymer or copolymer is between about 40° C. and about 70° C.,preferably between about 45° C. and about 65° C., and most preferablybetween about 50° C. and about 60° C., according to ASTM D3417. Inembodiments of the invention, the melt index of the polylactidehomopolymer or copolymer is at least about between about 50 g/10 min at210° C. using a 2.16 kg weight, preferably at least about 55 g/10 min at210° C. using a 2.16 kg weight, and most preferably at least about 60g/10 min at 210° C. using a 2.16 kg weight and at most it has a meltindex of at most about 500 g/10 min at 210° C. using a 2.16 kg weight,preferably at most about 200 g/10 min at 210° C. using a 2.16 kg weight,more preferably at most about 150 g/10 min at 210° C. using a 2.16 kgweight, and most preferably at most about 100 g/10 min at 210° C. usinga 2.16 kg weight, all in accordance with ASTM Method D1238. In all casesherein, where multiple values are provided for a lower limit andmultiple values are provided for an upper limit for any property orconcentration range, the invention contemplates any range extending fromand including any of the lower limits to and including any of the upperlimits.

An exemplary polylactide homopolymer or copolymer is the Vercet line ofresins, especially Vercet A1000, commercially available from NatureWorks LLC. This is a thermoplastic resin derived from annually renewableresources, is available in pellet form, and is an amorphous,low-melting, high-flow resin.

The hot melt adhesive composition further comprises a sulfonatedcopolyester. In embodiments of the invention, the specific gravity ofthe sulfonated copolyester is between about 1 and about 1.5 g/cm³,preferably between about 1.1 and about 1.3 g/cm³, and most preferablybetween about 1.2 and about 1.3 g/cm³, according to ASTM D792. Inembodiments of the invention, the glass transition temperature of thesulfonated copolyester is between about 30° C. and about 70° C.,preferably between about 35° C. and about 60° C., and most preferablybetween about 40° C. and about 50° C., according to a test using DSC inaccordance with ASTM E1356-08 in which the inflection point isdetermined, namely the midpoint in the inflection (second ordertransition) during the second heat cycle. In embodiments of theinvention, the intrinsic viscosity of the sulfonated copolyester isbetween about 0.15 dl/g and about 0.45 dl/g, preferably between about0.2 dl/g and about 0.4 dl/g, and most preferably between about 0.25 dl/gand about 0.35 dl/g, according to ASTM D5225-14. In embodiments of theinvention, the acid number of the sulfonated copolyester is either zeroor at least about 0.01 mg KOH/g and preferably at least about 0.1 mgKOH/g, and at most about 10 mg KOH/g, preferably at most about 5 mgKOH/g, and most preferably at most about 3 mg KOH/g. In embodiments ofthe invention, the hydroxyl number of the sulfonated copolyester iseither zero or at least about 0.01 mg KOH/g and preferably at leastabout 0.1 mg KOH/g, and at most about 15 mg KOH/g, preferably at mostabout 10 mg KOH/g, and most preferably at most about 5 mg KOH/g. Inembodiments of the invention, the sulfonated copolyester has a weightaverage molecular weight of between about 20,000 g/mol to 80,000 g/mol,preferably between about 25,000 g/mol and 60,000 g/mol, and mostpreferably between about 28,000 g/mol and 42,000 g/mol. The viscosity ofthe polyester is preferably between 1000 cP and 100,000 cP at 350° F.,most preferably between 5000 and 60,000 cP. Viscosity is measured in aBrookfield viscometer using a #27 spindle. Viscosity is generallyrelated to molecular weight with higher viscosities corresponding tohigher molecular weights.

According to embodiments of the invention, the sulfonated copolyestermay be selected those described in U.S. Pat. No. 6,410,627, incorporatedherein by reference. This patent describes a condensation polymercomprising the reaction product of:

-   -   a. at least one difunctional dicarboxylic acid or corresponding        methyl ester which is not a sulphomonomer;    -   b. 2 to 25 mole percent of at least one sulphomonomer containing        at least one metallic sulfonate group or nitrogen-containing        non-metallic sulfonate group attached to an aromatic or        cycloaliphatic nucleus and at least one functional group        selected from the group consisting of hydroxyl, carboxyl, and        amino;    -   c. at least one difunctional reactant selected from a glycol or        a mixture of a glycol and diamine having two —NRH groups, the        glycol containing two —C(R1)2-OH groups wherein R in the        reactant is hydrogen or an alkyl group of 1 to 6 carbon atoms,        and R1 in the reactant is a hydrogen atom, an alkyl of 1 to 5        carbon atoms, or an aryl group of 6 to 10 carbons atoms;    -   d. 0 to 40 mole percent of a difunctional reactant selected from        hydroxycarboxylic acids having one —C(R)2-OH group,        aminocarboxylic acids having one —NRH group, amino-alcohols        having one —C(R)2-OH group and one —NRH group, or mixtures of        said difunctional reactants wherein R in the reactant is        hydrogen or an alkyl group of 1 to 6 carbon atoms; and    -   e. 0 to 40 mole percent of a multifunctional reactant containing        at least three functional groups selected from hydroxyl,        carboxyl, and mixtures thereof wherein at least a portion of the        multifunctional reactant contains at least three hydroxyl        groups,        wherein all stated mole percentages are based on the total of        all acid, hydroxyl and amino group containing reactants being        equal to 200 mole percent, and wherein the polymer contains        proportions of acid-group containing reactants (100 mole percent        acid) to hydroxy- and amino-group containing reactants (100 mole        percent base) such that the value of (equivalents) EQ (base)        divided by (equivalents) EQ (acid) is between 0.5 and 2. The        polyester composition used as a component of the hot melt        adhesives of the present invention preferably comprises 60 to        100 mole percent of (a), 4 to 20 mole percent of (b), 80 to 100        mole percent of (c), 0 to 10 mole percent of (d), and 0 to 20        mole percent of (e). In other more preferred embodiments of the        invention the polyester comprises 60 to 100 mole percent of        1,4-cyclohexanedicarboxylic acid; 4 to 20 mole percent of        5-sodiosulfoisophthalic acid or dimethyl        5-sodiosulfoisophthalate; and 80 to 100 mole percent of        diethylene glycol, neopentyl glycol or cyclohexanedimethanol.

According to embodiments of the invention, the sulfonated copolyestermay be selected from those described in U.S. Pat. Nos. 4,910,292,4,973,656 and 4,990,593, incorporated herein by reference. In stillanother embodiment of the invention, the sulfonated copolyestercomprises Vitel® 1831044 copolyester polymer commercially available fromBostik, Inc. Hot melt adhesives based on sulfonated copolyesters aredescribed in U.S. Pat. No. 5,750,605, incorporated herein by reference.Exemplary sulfonated copolyesters also include the Eastman AQ line ofsolid copolyesters commercially available from Eastman Chemical.

In embodiments of the invention, the sulfonated copolyester is waterdispersible. Water dispersibility may be measured by the ability of theresin to disperse and remain as a homogeneous dispersion after mixing.This characteristic can be determined by combining the product withwater under heat (e.g., 95° C.) and applying shear. The resin firstsoftens on heating (i.e., it is clear and amorphous then becomes cloudyand soft when mixed with water). A product is said to be waterdispersible if it does not settle or phase separate under the force ofgravity once the mixing is completed.

The use of sulfonated copolyester confers the additional advantage ofproviding a degree of water sensitivity which is dependent on the ionicstrength of the aqueous environment. Thus, adhesives can be formulatedwhich are sufficiently resistant to the ionic environments encounteredduring use (such as the exposure to bodily fluids encountered in diapersand feminine napkins) yet still disperse and/or debond in tap water,which is of lower ionic strength. These adhesives are thereforeparticularly useful in constructing compostable articles.

The hot melt adhesive composition further comprises a plasticizer.Preferably, the plasticizer is a solid plasticizer, which are especiallyuseful in embodiments requiring high heat resistance. The solidplasticizer may comprise a benzoate. The benzoate may be selected fromthe group consisting of glycerol tribenzoate, sucrose benzoate,pentaerythritol tetrabenzoate, and 1,4-cyclohexane dimethanoldibenzoate. Most preferably, the benzoate comprises, consistsessentially of, or consists of 1,4-cyclohexane dimethanol dibenzoate,commercially available from under the trademark Benzoflex 352,commercially available from Eastman Chemical. One of the deficiencies ofusing polylactide homopolymer or copolymer is poor heat resistanceproperties. The incorporation of solid plasticizer into the formulationhas been found to provide the heat resistance properties needed for useas an adhesive for disposable cups used for hot-beverages. Vegetablewax-based solid plasticizers may also be appropriate.

In one embodiment, the solid plasticizer has a melt point of betweenabout 80° C. and about 160° C., preferably between about 90° C. andabout 150° C., more preferably between about 100° C. and about 140° C.,still more preferably between about 110° C. and about 130° C., and mostpreferably between about 110° C. and about 125° C., according to ASTMD7138 using DSC. In embodiments of the invention, the acid number of thesolid plasticizer is either zero or at least about 0.001 mg KOH/g andpreferably at least about 0.01 mg KOH/g, and at most about 3 mg KOH/g,preferably at most about 1 mg KOH/g, and most preferably at most about0.2 mg KOH/g. In embodiments of the invention, the hydroxyl number ofthe sulfonated copolyester is either zero or at least about 0.01 mgKOH/g and preferably at least about 0.1 mg KOH/g, and at most about 10mg KOH/g, preferably at most about 5 mg KOH/g, and most preferably atmost about 3 mg KOH/g.

In embodiments of the invention, the adhesive further comprises a secondplasticizer. The second plasticizer is selected from the groupconsisting of ethylene glycol, propylene glycol, and polyethyleneglycol. Polyethylene Glycol having lower viscosities (such as PEG 400)serve to reduce the viscosity of the adhesive. In embodiments in which asolid plasticizer is used as the first plasticizer and the viscosity ofthe formulation is needed to be reduced, a liquid plasticizer isparticularly advantageous. A range of polyethylene glycols can be used,depending on the desired viscosity of the formulation.

Other plasticizers suitable for use in the hot melt adhesive compositionare described in U.S. Pat. No. 5,753,724, incorporated herein byreference. Plasticizers can improve the melt properties of theadhesives, can impart pressure sensitive properties, can extend theadhesive reducing cost, and can increase the flexibility and meltproperties of the hot melt adhesive. The preferred plasticizers for usewith the hot melt adhesives of the invention arebiodegradable/compostable plasticizers. Such plasticizers typicallycomprise naturally recurring oils or synthetic materials manufacturedcontaining ester or urea carbamyl or amido groups. Plasticizerstypically have different molecular weight than the other constituents ofthe adhesive composition. When a solid plasticizer is used as the firstplasticizer and the viscosity of the formulation is needed to bereduced, liquid plasticizers are used, such as materials having amolecular weight less than about 5,000 g/mol, preferably less than 1,000g/mol, that can provide plasticizer properties to the compositions ofthe invention. Preferred classes of plasticizer materials for use in theinvention comprise natural fats and oils compatible with the otherconstituents disclosed herein. A further preferred class of plasticizersfor use in the adhesives of the invention include ester plasticizerstypically made by reacting aromatic or aliphatic small molecule mono-,di- or triols with an aromatic or aliphatic acid compositions. Specificexamples of additional plasticizers include castor oil, TegMer 809-PEG400 di-2-ethylhexoate ester, Plasthall DBS-dibutyl sebacate, PlasthallDIBA diisobutyl sebacate, Santizer 160, which is a butyl benzylphthalate, polycaprolactone diols having a molecular weight of about 500g/mole and a melting point less than about 25° C., ethylene glycoldibenzoate, propylene glycol dibenzoate, diethylene glycol dibenzoate,and dipropylene glycol dibenzoate.

In embodiments of the invention, the adhesive further comprises astabilizer or an anti-oxidant. The stabilizers/anti-oxidants which areuseful in the hot melt adhesive compositions of the present inventionare incorporated to help protect the other constituents noted above, andthereby the total adhesive system, from the effects of thermal andoxidative degradation which normally occur during the manufacture andapplication of the adhesive as well as in the ordinary exposure of thefinal product to the ambient environment. The anti-oxidant may comprisea hindered phenol. The hindered phenol may be selected from the groupconsisting of1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;pentaerythritoltetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; n-octadecyl3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4′-methylenebis(2,6-di-tert-butylphenol); 4,4′-thiobis (6-tertbutyl-o-cresol);2,6-di-tert-butylphenol;6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine;di-n-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate;2-(n-octylthio)-ethyl 3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitolhexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. The hot meltadhesive of the present invention may also include a stabilizer and/oran antioxidant in an effective amount, preferably in an amount of fromabout 0.1% to about 5% by weight. Preferably, from about 0.1% to 2% of astabilizer or antioxidant is incorporated into the composition. Amongthe applicable stabilizers are hindered phenols and multifunctionphenols, such as sulfur and phosphorous-containing phenols.

Polyolefin nucleating agents may also be also present in the adhesive ofthe invention. Nucleating agents suitable for this invention aregenerally of the sub class of nucleating agents known as clarifyingagents that are commonly employed in polyolefin additive packages topromote rapid crystallization. Suitable materials include dibenzylidenesorbitol derivatives such as Millad 3988 and Millad NX8000 supplied byMilliken as well as Irgaclear D produced by BASF. Other suitable agentsinclude aromatic amide systems such as NJ Star NU-100 provided by NewJapan Chemical Company. If included, the nucleating agent is generallypresent in the adhesive compositions in amounts of about 0.05 to 5% byweight of the composition, preferably about 0.1 to 2.5% by weight areutilized, and most preferably about 0.2 to 1.0% by weight. Blends of twoor more nucleating agent may also be used. For example, a blend of anucleating agent and a second nucleating agent that is different thanthe first nucleating agent may also be employed. From about 0.05% toabout 5% by weight of one or more additional nucleating agent may beblended together with the first nucleating agent if desired. Thenucleating agent may be used directly as a powder, as a slurry in aportion of suitable plasticizing agent, or as a component in amasterbatch of suitable polymer masterbatch such as Milliken NX-10.Nucleation packages such as those described in US 2015/0299526 can alsobe included to tailor the set up rate and bonding properties of thehot-melt adhesive.

It should be understood that other optional additives may beincorporated into the adhesive composition of the present invention inorder to modify particular physical properties. These may include, forexample, such materials as ultraviolet light (UV) absorbers, waxes,surfactants, inert colorants, titanium dioxide, fluorescing agents andfillers. Typical fillers include talc, calcium carbonate, clay silica,mica, wollastonite, feldspar, aluminum silicate, alumina, hydratedalumina, glass microspheres, ceramic microspheres, thermoplasticmicrospheres, baryte and wood flour and may be included in an amount upto 40% by weight, and preferably between 1 and 30% by weight.

The adhesive of the present invention is compostable. As used herein,the term “compostable” as applied to an adhesive is an adhesive whichmeets the requirements of either: (1) the Disintegration Testing asdefined by ASTM D 6400-12 (using ISO 20200) (84 day compost exposure) or(2) the Aerobic Biodegradation as defined by ASTM D 6400-12 (using ASTM5338-15) (at 58±2° C. at 141 days). In other words, the adhesive willreach a minimum of 90% weight loss within 84 days under theDisintegration Testing conditions or will have reached at least 90%carbon conversion (based on CO₂ production) within 141 days according tothe Aerobic Biodegradation testing, described in more detail in theexamples. In preferred embodiments, the adhesive meets the requirementsof both: (1) the Disintegration Testing as defined by ASTM D 6400-12(using ISO 20200) (84 day compost exposure) and (2) the AerobicBiodegradation as defined by ASTM D 6400-12 (using ASTM 5338-15) (at58±2° C. at 141 days).

The relative amounts of the various constituents have been found to beimportant for the adhesive to achieve the various properties needed forthe desired application. This has been found to be especially true whenthe adhesive is to be used to seal the two walls together in a beveragecup, which requires heat resistance, resistance over a wide range oftemperatures, and compostability. In an embodiment, the polylactic acid,the sulfonated copolyester and the plasticizer are present in amountseffective to achieve a bond performance of at least 80%, preferably atleast 90%, and most preferably 100%. As used herein, “bond performance”refers to the performance of the adhesive when applied to uncoatedpaperboard and tested in the manner as follows: The corrugated flapswere cut into 1.5″×4″ coupons. The adhesives were applied at 350° F. ina ⅜″ bead with two seconds open time and two seconds compression. Bondswere allowed to set at room temperature overnight. Three bonds made witheach adhesive were placed in a 0° F. freezer and a 160° F. oven for 24hours. At that time, the bonds were tested immediately upon removal forpercentage fiber tear. “Fiber tear” refers to areas of the substratethat were torn, as opposed to areas where the adhesive failed, eitheradhesively or cohesively. In preferred embodiments, the polylactic acid,the sulfonated copolyester and the solid plasticizer are present inamounts effective achieve the above-referenced bond performance at atemperature of about 175° F., most preferably over a range oftemperatures from 0° F. to 175° F. In other embodiments, wherein thepolylactic acid and the sulfonated copolyester are present in a weightratio of between about 1:1 and about 9:5 by weight, preferably betweenabout 6:5 and about 8:5 by weight, and most preferably between about13:10 and about 3:2 by weight.

According to embodiments of the invention, the formulation includes thefollowing constituents in approximately the following weightpercentages:

-   -   the polylactic acid is present in an amount to function as a        base polymer to provide cohesion for the adhesive and in        embodiments is present in an amount of between about 25 and        about 43% by weight, preferably between about 30 and about 38%        by weight, and most preferably between about 31 and about 37% by        weight;    -   the sulfonated copolyester is present in an amount effective to        function as an adhesion promoter to porous substrates, such as        paperboard or a label, and in embodiments is present in an        amount of between about 15 and about 35% by weight, preferably        between about 20 and about 30% by weight, and most preferably        between about 22 and about 28% by weight;    -   the plasticizer is present in an amount effective to improve the        heat resistance of the formulation to the desired level (e.g.,        to the bond performance referred to above at high temperatures),        and in embodiments is present in an amount of between about 5        and about 60% by weight, preferably between about 15 and about        55% by weight, more preferably between about 20 and about 50% by        weight, and most preferably between about 36 and about 42% by        weight; and    -   If used, a second plasticizer is present in an amount effective        to reduce the viscosity of the adhesive to the desired values        and in embodiments in present in an amount of between about 1        and 5% by weight, preferably between about 1.3 and about 3% by        weight, and most preferably between about 1.5 and about 2% by        weight.    -   If used, an anti-oxidant, such as a hindered phenol, is present        in an amount effective to prevent oxidation or stabilize the        adhesive and in embodiments is present in an amount of between        about the anti-oxidant is present in an amount of between about        0.1 and about 1% by weight, preferably between about 0.25 and        about 0.75% by weight, and most preferably between about 0.4 and        about 0.6% by weight.

Preferably, the composition does not contain more than 5 wt %, morepreferably no more than about 4 wt %, and most preferably no more thanabout 3 wt % of a constituent having a hydroxyl number greater than 100mg KOH/g. Such a constituent could be, for example, styrene allylcopolymers, orthophthalate neopentyl glycol, polyester polyols, orcombinations thereof, as disclosed in U.S. Pat. No. 6,410,627,incorporated herein by reference.

There is no particular order in making an adhesive composition of thepresent invention, and it may be made using conventional process steps.The adhesive may be made by mixing the various constituents and thenheating just before application to a substrate.

The viscosity of the adhesive material according to the presentinvention should be generally at a viscosity at the applicationtemperature appropriate to be processed and applied to its substrate asa hot melt adhesive. An adhesive with relatively low viscosity at a lowapplication temperature is needed to be processed through standard hotmelt adhesive equipment and to achieve the desired pattern andconsequently suitable bonding performance at the applicationtemperature. In general, the viscosity is equal to or less than about50,000 cP at application temperature, preferably equal to or less thanabout 40,000 cP at application temperature, even more preferably lessthan about 35,000 cP at application temperature, still more preferablyless than about 30,000 cP at application temperature according to ASTMD3236. All viscosities identified herein are measured according to thismodified ASTM standard. Preferably, the viscosity of the composition isat least 1,000 cP, more preferably at least 5,000 cP, still morepreferably at least about 7,500 cP and most preferably at least about15,000 cP, at application temperature. Thus the viscosity could bebetween 1,000 cP and 35,000 cP and between 5,000 cP and 20,000 cP at121° C. In other embodiments, the viscosity of the composition isbetween any of the ranges contemplated herein at various typically usedapplication temperatures, the value of which depends on the particularapplication of the adhesive, between 121° C. at 180° C., such as at 121°C., 127° C., 135° C., 149° C. and 177° C. In an embodiment in which theadhesive is used to bond a double-walled cup for hot beverages, theviscosity of the adhesive at 177° C. is preferably between about 5,000cP and about 50,000 cP, more preferably between about 15,000 cP andabout 35,000 cP, and most preferably between about 20,000 cP and about30,000 cP.

The end use application requirements are an important consideration inidentifying the desired softening point of the adhesive formulation. Forthe application of using the adhesive to bond a double-walled cup for ahot beverage, the Ring and Ball softening point of the adhesive asdetermined by ASTM E28-99 may be between about 180° F. and about 300°F., more preferably between about 200° F. and about 280° F., and mostpreferably between about 220° F. and about 260° F.

The hot melt adhesive may be applied to the substrate(s) using a varietyof coating techniques. Examples include hot melt slot die coating, hotmelt wheel coating, hot melt roller coating, melt-blown coating as wellas slot, spiral spray, and wrapping spray methods such as those used toaffix elastic strands. Spray techniques are numerous and can be donewith or without assistance of compressed air that would shape theadhesive spray pattern. The hot melt adhesive material is generallypumped molten through hoses to the final coating spot on the substrates.

In an embodiment of the invention, a method for forming a double-walledcontainer comprises the steps of:

-   -   (a) applying the hot melt adhesive composition described herein        in a molten state to the outer surface of a first generally        cylindrical paperboard substrate;    -   (b) mating a generally rectangular second paperboard substrate        to the first paperboard substrate, wherein the second paperboard        substrate is longer than the circumference of the first        paperboard substrate, thereby providing an axial strip at which        the ends of the second paperboard substrate overlap; and    -   (c) applying the hot melt adhesive composition in a molten state        to one of the mating surfaces of the axial strip; and    -   (d) mating the mating surfaces of the axial strip to provide the        double-walled container.

In an embodiment of the invention, step (a) comprises applying the hotmelt adhesive in a radial pattern. In other embodiments, steps (a) and(c) comprise applying the hot melt adhesive composition in the form of abead. Preferably, the paperboard is compostable. Still more preferably,the paperboard used for the container is compostable and the containeris a beverage cup. One such double-walled container is described in U.S.Pat. No. 6,109,518, incorporated herein by reference.

The compostable hot melt adhesive of the present invention may be usedin a number of applications, especially ones in which the final article,including the adhesive, is desired to be compostable. As discussedabove, embodiments of the adhesive of the present invention areespecially appropriate for dual-walled paperboard beverage cups.Exemplary other applications involve case and carton applications, usewith burlap or other compostable substrates for tree bulbs or plantseeds, and use with other compostable films. In each of these, theadhesive is applied to a first substrate in a molten state, a secondsubstrate (or a portion of the first substrate) is then contacted withthe adhesive, which is then allowed to cool and thereby bond the firstsubstrate to the second substrate (or the other portion of the firstsubstrate folded onto and mated with the first substrate). For example,in one embodiment, a tree bulb or plant seed may be wrapped incompostable burlap, adhesive may be applied to a mating area of theburlap, and the burlap is then folded over onto itself such that twomating surfaces of the burlap become bonded to one another upon coolingof the hot melt adhesive. In another embodiment, a first compostablefilm or substrate is contacted with the adhesive of the presentinvention, then a second compostable film is contacted with theadhesive, which is allowed to cool thereby bonding the two compostablefilms together to form a compostable laminate.

ASPECTS OF THE INVENTION

-   -   Aspect 1. A hot melt adhesive composition comprising:    -   (a) a polylactide homopolymer or copolymer;    -   (b) sulfonated copolyester; and    -   (c) a plasticizer,    -   wherein the adhesive is compostable.    -   Aspect 2. The composition of Aspect 1, wherein the polylactide        homopolymer or copolymer is selected from the group consisting        of polylactic acid and copolymers of lactones, preferably        glycolide and caprolactone.    -   Aspect 3. The composition of Aspect 1, wherein the polylactide        homopolymer or copolymer comprises, consists essentially of, or        consists of polylactic acid.    -   Aspect 4. The composition of any of Aspects 1-3, wherein the        polylactic acid, the sulfonated copolyester and the plasticizer        are present in amounts effective to achieve a bond performance        of at least 80%, preferably at least 90%, and most preferably        100%.    -   Aspect 5. The composition of Aspect 4, wherein the polylactic        acid, the sulfonated copolyester and the solid plasticizer are        present in amounts effective achieve the bond performance at a        temperature of about 175° F., most preferably over a range of        temperatures from 0° F. to 175° F.    -   Aspect 6. The composition of any of Aspects 1-5, wherein the        polylactide homopolymer or copolymer and the sulfonated        copolyester are present in a weight ratio of between about 1:1        and about 9:5 by weight, preferably between about 6:5 and about        8:5 by weight, and most preferably between about 13:10 and about        3:2 by weight.    -   Aspect 7. The composition of any of Aspects 1-6, wherein:    -   (a) the polylactide homopolymer or copolymer is present in an        amount of between about 25 and about 43% by weight, preferably        between about 30 and about 38% by weight, and most preferably        between about 31 and about 37% by weight;    -   (b) the sulfonated copolyester is present in an amount of        between about 15 and about 35% by weight, preferably between        about 20 and about 30% by weight, and most preferably between        about 22 and about 28% by weight; and    -   (c) the plasticizer is present in an amount of between about 5        and about 60% by weight, preferably between about 15 and about        55% by weight, more preferably between about 20 and about 50% by        weight, and most preferably between about 36 and about 42% by        weight.    -   Aspect 8. The composition of any of Aspects 1-7, wherein the        sulfonated copolyester is water-dispersible.    -   Aspect 9. The composition of any of Aspects 1-8, wherein the        plasticizer comprises a solid plasticizer.    -   Aspect 10. The composition of Aspect 9, wherein the solid        plasticizer comprises a benzoate.    -   Aspect 11. The composition of Aspect 10, wherein the benzoate is        selected from the group consisting of glycerol tribenzoate,        sucrose benzoate, pentaerythritol tetrabenzoate, and        1,4-cyclohexane dimethanol dibenzoate.    -   Aspect 12. The composition of Aspect 10, wherein the benzoate        comprises, consists essentially of, or consists of        1,4-cyclohexane dimethanol dibenzoate.    -   Aspect 13. The composition of any of Aspects 1-12 further        comprising a second plasticizer.    -   Aspect 14. The composition of Aspect 13, wherein the second        plasticizer is selected from the group consisting of ethylene        glycol, propylene glycol, and polyethylene glycol.    -   Aspect 15. The composition of Aspects 13 or 14, wherein the        second plasticizer is present in an amount of between about 1        and 5% by weight, preferably between about 1.3 and about 3% by        weight, and most preferably between about 1.5 and about 2% by        weight.    -   Aspect 16. The composition of any of Aspects 1-15 further        comprising an anti-oxidant.    -   Aspect 17. The composition of Aspect 16, wherein the        anti-oxidant comprises, consists essentially of, or consists of        a hindered phenol.    -   Aspect 18. The composition of Aspect 17, wherein the hindered        phenol is selected from the group consisting of        1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;        pentaerythritol        tetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;        n-octadecyl 3,5-di-tert-butyl-4-hydroxyphenyl) propionate;        4,4′-methylenebis (2,6-di-tert-butylphenol); 4,4′-thiobis        (6-tertbutyl-o-cresol); 2,6-di-tert-butylphenol;        6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine;        di-n-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate;        2-(n-octylthio)-ethyl 3,5-di-tert-butyl-4-hydroxybenzoate; and        sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].    -   Aspect 19. The composition of any of Aspects 16-18, wherein the        anti-oxidant is present in an amount of between about 0.1 and        about 1% by weight, preferably between about 0.25 and about        0.75% by weight, and most preferably between about 0.4 and about        0.6% by weight.    -   Aspect 20. The composition of any of Aspects 1-19, wherein the        composition does not contain more than 5 wt %, more preferably 4        wt %, and most preferably 3 wt % of a constituent having a        hydroxyl number greater than 100 mg KOH/g.    -   Aspect 21. The composition of any of Aspects 1-20, wherein the        sulfonated copolyester has a weight average molecular weight of        between about 20,000 g/mol to 80,000 g/mol, preferably between        about 25,000 g/mol and 60,000 g/mol, and most preferably between        about 28,000 g/mol and 42,000 g/mol.    -   Aspect 22. The composition of any of Aspects 1-21, wherein the        polylactide homopolymer or copolymer has a melt index of at        least 50, preferably at least 55, and most preferably at least        60 g/10 min at 210° C. using a 2.16 kg weight in accordance with        ASTM Method D1238.    -   Aspect 23. The composition of any of Aspects 1-22, wherein        adhesive meets the requirements of both: (1) the Disintegration        Testing as defined by ASTM D 6400-12 (using ISO 20200) and (2)        the Aerobic Biodegradation as defined by ASTM D 6400-12 (using        ASTM 5338-15).    -   Aspect 24. The composition of any of Aspects 1-23, wherein the        adhesive has a Ring and Ball softening point as determined by        ASTM E28-99 of between about 180° F. and about 300° F., more        preferably between about 200° F. and about 280° F., and most        preferably between about 220° F. and about 260° F.    -   Aspect 25. A method for forming a double-walled container        comprising the steps of:    -   (a) applying the hot melt adhesive composition of any of Aspects        1-24 in a molten state to the outer surface of a first generally        cylindrical paperboard substrate;    -   (b) mating a generally rectangular second paperboard substrate        to the first paperboard substrate, wherein the second paperboard        substrate is longer than the circumference of the first        paperboard substrate, thereby providing an axial strip at which        the ends of the second paperboard substrate overlap; and    -   (c) applying the hot melt adhesive composition in a molten state        to one of the mating surfaces of the axial strip; and    -   (d) mating the mating surfaces of the axial strip to provide the        double-walled container.    -   Aspect 26. The method of Aspect 25, wherein step (a) comprises        applying the hot melt adhesive in a radial pattern.    -   Aspect 27. The method of Aspects 25 or 26, wherein steps (a)        and (c) comprise applying the hot melt adhesive composition in        the form of a bead.    -   Aspect 28. The method of any of Aspects 25-27, wherein the        paperboard is compostable.    -   Aspect 29. The container formed by the method of any of Aspects        25-28.    -   Aspect 30. The container of Aspect 29, wherein the paperboard        used for the container is compostable and the container is a        beverage cup.

Examples

The following examples demonstrate several aspects of certain preferredembodiments of the present invention, and are not to be construed aslimitations thereof.

The feasibility of using adhesives according to the present inventionfor a double-walled beverage cup was investigated. In particular, threeformulations were tested for bond performance according to the criteriadescribed below.

The constituents of the adhesive, shown below in Table 1, were mixed atroom temperature and then heated. The molten adhesive was heated to 350°F. and then applied in radial beads to the outer, uncoated paperboardwall of a cup. An outer wall of a commercially available paperboard cupwas adhered to the inner wall by mating the outer wall to the adhesivejust applied to the inner wall. Another radial bead was applied to oneof the mating surfaces of the second wall at a portion of the secondwall which overlapped itself, creating an axial strip. The second wallwas then adhered to itself by mating the mating surfaces of the axialstrip. The radial bead (adhesive around the inner wall of the cup) tocreates a gap between the inner wall and outer wall to provideinsulation. The adhesive was applied at 350° F. using conventionaladhesive application equipment.

Adhesive bond strength was measured by peeling apart the end seals tocheck for 100% fiber tear (i.e., only the walls themselves tore, and theadhesive did not fail) and heat resistant performance was tested bypouring hot water in the cup immediately after application of theadhesive for 1 minute. The end seal must have no delamination from topto bottom seal to pass the test. Adhesive bond strength at 0° F. andboiling water conditions compared to the current traditional hot meltadhesives, shown in the control.

The constituents used, as identified in Table 1, were a polylactic acidsold under the trademark Vercet A1000 by Nature Works LLC (“PLA”); asulfonated copolyester sold under the trademark VitelD1831044 by Bostik,Inc. (“Sulfonated Copolyester”); a solid plasticizer sold under thetrademark Benzoflex 352 by Eastman Chemical (“Solid plasticizer”); aliquid plasticizer sold under the trademark Carbowax Sentry PEG 400 byDow Chemical; and a conventional antioxidant (“AO”). Table 1 sets forththe weight (in grams) of the various constituents. As shown, Formulation1 had about 30 wt % of the solid plasticizer. Formulation 1 did not passthe hot water test desired for this application. Formulation 2, whichhad more solid plasticizer than Formulation 1 but no liquid plasticizer,also in contrast to Formulation 1, had very good adhesion immediatelyoff-line and passed hot water testing. However, after ten minutes atroom temperature, the adhesive became brittle and adhesively failed bothin radial and end seal applications. Formulation 3 passed the adhesivebond strength test both off line and aged (1 day, 5 days, and 2 monthsat various temperatures 0, 40, 72, 140, 160° F.).

In addition, Mix 3 surprisingly showed wider service temperatureperformance (0° F.-160° F.), and boiling water conditions (microwave for3.0 minutes, around 210° F. water temperature). Although Formulations 1and 2 did not meet the rigorous requirements of this application (i.e.,for cups for hot beverages), these formulations may be appropriate forother applications requiring compostable adhesives.

TABLE 1 Solid Liquid Soft- Formu- Sulfonated Plasti- Plasti- eninglation PLA Copolyester cizer cizer A0 Total Point 1 39.1 20.6 30.3 10.00.5 100.5 240.0 2 40.0 20.0 40.0 0.0 0.5 100.5 246.0 3 34.0 25.1 39.21.7 0.5 100.5 248.0

An analysis was carried to determine whether the adhesive composition ofFormulation 3 met requirements of the Disintegration Testing as definedby ASTM D 6400-12 (using ISO 20200). In particular, drawn down films ofthis adhesive with a maximum thickness of 31.5 mg were evaluated usingISO 20200 per ASTM D 6400-12 for up to eighty-four days at 58±2° C. Thecomposting material of the test had a carbon-to-nitrogen ratio of 30:1,which is within the specifications for this test. The pH of the compostmaterial at the start of testing was approximately 7.0 with a total drysolids content of 44.5% when dried at 105° C. until constant weight. Themature mushroom compost used in the test was purchased from MontereyMushrooms in Princeton, Ill. and, as received, had a C:N ratio of 13:1.To meet this requirement, the sample being tested must reach a minimumof 90% weight loss within 84 days of testing. The adhesive sample testedwas completely disintegrated (100% weight loss) after 84 days.

An analysis was carried to determine whether the adhesive composition ofFormulation 3 met requirements of the Aerobic Biodegradation as definedby ASTM 5338-15. In particular, the ASTM D 6400-12 mineralization of anadhesive sample exposed to Aerobic Biodegradation using ASTM D-5338-15mineralization at 58±2° C. (tier two level testing) through contact withcompost medium was evaluated. The lab feedstock compost of the test hada C:N ratio of 29:1, which is within the specifications for this test.The pH of the compost material at the start of testing was approximately7.0 with a total dry solids content of 50.0% when dried at 105° C. untilconstant weight. The mature mushroom compost used in the test waspurchased from Monterey Mushrooms in Princeton, Ill. and, as received,had a C:N ratio of 14:1. To meet this requirement, the sample beingtested must reach a minimum of 70% carbon conversion within forty-five(45) days per ASTM D 5338-15 Mineralization and 90% carbon conversionwithin one hundred forty-one (141) days per ASTM D 5338-15Mineralization. The adhesive sample tested met both of theserequirements, including reaching an average of 91.83% carbon conversionin 141 days.

Where a range of values is provided, it is understood that eachintervening value, and any combination or sub-combination of interveningvalues, between the upper and lower limit of that range and any otherstated or intervening value in that stated range, is encompassed withinthe range of values recited. In addition, the invention includes a rangeof a constituent which is the lower limit of a first range and an upperlimit of a second range of that constituent.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art to which this invention belongs. All publications and patentsspecifically mentioned herein are incorporated by reference in theirentirety for all purposes including describing and disclosing thechemicals, instruments, statistical analyses and methodologies which arereported in the publications which might be used in connection with theinvention. Nothing herein is to be construed as an admission that theinvention is not entitled to antedate such disclosure by virtue or priorinvention.

Although illustrated and described herein with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the spirit of the invention.

We claim:
 1. A hot melt adhesive composition comprising: (a) apolylactide homopolymer or copolymer; (b) sulfonated copolyester; and(c) a plasticizer, wherein the adhesive is compostable.
 2. Thecomposition of claim 1, wherein the polylactide homopolymer or copolymeris selected from the group consisting of polylactic acid and copolymersof lactones, preferably glycolide and caprolactone.
 3. The compositionof claim 1, wherein the polylactide homopolymer or copolymer comprisespolylactic acid.
 4. The composition of claim 3, wherein the polylacticacid, the sulfonated copolyester and the plasticizer are present inamounts effective to achieve a bond performance of at least 80%,preferably at least 90%, and most preferably 100%.
 5. The composition ofclaim 4, wherein the polylactic acid, the sulfonated copolyester and thesolid plasticizer are present in amounts effective achieve the bondperformance at a temperature of about 175° F., most preferably over arange of temperatures from 0° F. to 175° F.
 6. The composition of claim3, wherein the polylactic acid and the sulfonated copolyester arepresent in a weight ratio of between about 1:1 and about 9:5 by weight,preferably between about 6:5 and about 8:5 by weight, and mostpreferably between about 13:10 and about 3:2 by weight.
 7. Thecomposition of claim 3, wherein: (a) the polylactic acid is present inan amount of between about 25 and about 43% by weight, preferablybetween about 30 and about 38% by weight, and most preferably betweenabout 31 and about 37% by weight; (b) the sulfonated copolyester ispresent in an amount of between about 15 and about 35% by weight,preferably between about 20 and about 30% by weight, and most preferablybetween about 22 and about 28% by weight; and (c) the plasticizer ispresent in an amount of between about 5 and about 60% by weight,preferably between about 15 and about 55% by weight, more preferablybetween about 20 and about 50% by weight, and most preferably betweenabout 36 and about 42% by weight.
 8. The composition of claim 1, whereinthe sulfonated copolyester is water-dispersible.
 9. The composition ofclaim 1, wherein the plasticizer comprises a solid plasticizer.
 10. Thecomposition of claim 9, wherein the solid plasticizer comprises abenzoate.
 11. The composition of claim 10, wherein the benzoate isselected from the group consisting of glycerol tribenzoate, sucrosebenzoate, pentaerythritol tetrabenzoate, and 1,4-cyclohexane dimethanoldibenzoate.
 12. The composition of claim 10, wherein the benzoatecomprises 1,4-cyclohexane dimethanol dibenzoate.
 13. The composition ofclaim 1 further comprising a second plasticizer.
 14. The composition ofclaim 13, wherein the second plasticizer is selected from the groupconsisting of ethylene glycol, propylene glycol, and polyethyleneglycol.
 15. The composition of claim 13, wherein the second plasticizeris present in an amount of between about 1 and 5% by weight, preferablybetween about 1.3 and about 3% by weight, and most preferably betweenabout 1.5 and about 2% by weight.
 16. The composition of claim 1 furthercomprising an anti-oxidant.
 17. The composition of claim 16, wherein theanti-oxidant comprises a hindered phenol.
 18. The composition of claim17, wherein the hindered phenol is selected from the group consisting of1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;pentaerythritoltetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; n-octadecyl3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4′-methylenebis(2,6-di-tert-butylphenol); 4,4′-thiobis (6-tertbutyl-o-cresol);2,6-di-tert-butylphenol;6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine;di-n-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate;2-(n-octylthio)-ethyl 3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitolhexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].
 19. Thecomposition of claim 16, wherein the anti-oxidant is present in anamount of between about 0.1 and about 1% by weight, preferably betweenabout 0.25 and about 0.75% by weight, and most preferably between about0.4 and about 0.6% by weight.
 20. The composition of claim 1, whereinthe composition does not contain more than 5 wt %, more preferably 4 wt%, and most preferably 3 wt % of a constituent having a hydroxyl numbergreater than 100 mg KOH/g.
 21. The composition of claim 1, wherein thesulfonated copolyester has a weight average molecular weight of betweenabout 20,000 g/mol to 80,000 g/mol, preferably between about 25,000g/mol and 60,000 g/mol, and most preferably between about 28,000 g/moland 42,000 g/mol.
 22. The composition of claim 1, wherein thepolylactide homopolymer or copolymer has a melt index of at least 50,preferably at least 55, and most preferably at least 60 g/10 min at 210°C. using a 2.16 kg weight in accordance with ASTM Method D1238.
 23. Thecomposition of claim 1, wherein adhesive meets the requirements of both:(1) the Disintegration Testing as defined by ASTM D 6400-12 (using ISO20200) and (2) the Aerobic Biodegradation as defined by ASTM D 6400-12(using ASTM 5338-15).
 24. The composition of claim 1, wherein theadhesive has a Ring and Ball softening point as determined by ASTME28-99 of between about 180° F. and about 300° F., more preferablybetween about 200° F. and about 280° F., and most preferably betweenabout 220° F. and about 260° F.
 25. A method for forming a double-walledcontainer comprising the steps of: (a) applying the hot melt adhesivecomposition of claim 1 in a molten state to the outer surface of a firstgenerally cylindrical paperboard substrate; (b) mating a generallyrectangular second paperboard substrate to the first paperboardsubstrate, wherein the second paperboard substrate is longer than thecircumference of the first paperboard substrate, thereby providing anaxial strip at which the ends of the second paperboard substrateoverlap; and (c) applying the hot melt adhesive composition in a moltenstate to one of the mating surfaces of the axial strip; and (d) matingthe mating surfaces of the axial strip to provide the double-walledcontainer.
 26. The method of claim 25, wherein step (a) comprisesapplying the hot melt adhesive in a radial pattern.
 27. The method ofclaim 25, wherein steps (a) and (c) comprise applying the hot meltadhesive composition in the form of a bead.
 28. The method of claim 25,wherein the paperboard is compostable.
 29. The container formed by themethod of claim
 25. 30. The container of claim 29, wherein thepaperboard used for the container is compostable and the container is abeverage cup.